1. Field of the Invention
The present invention relates to a method of and an apparatus for dispersing image data on a recording medium in an auxiliary scanning direction to record an image on the recording medium when the recording medium is scanned in a main scanning direction while it is being fed in the auxiliary scanning direction.
2. Description of the Related Art
There have heretofore been widely used image recording apparatus for recording an image on a recording medium with a thermal head, a laser beam, etc. In such an image recording apparatus, a thermosensitive recording medium is pressed against a linear thermal head composed of a one-dimensional array of heating elements, for example, and the thermosensitive recording medium is fed in a direction substantially normal to the one-dimensional array of heating elements while at the same time the heating elements are being individually controlled depending on supplied image data, thereby recording a desired two-dimensional gradation image on the thermosensitive recording medium.
Such a gradation image is formed as shown in FIG. 17A of the accompanying drawings. An image having a density D=1 is formed by heating a heating element for t seconds. An image having a density D=2 is formed by heating a heating element for 2t seconds. Similarly, images having respective densities D=3.about.5 are formed by heating a heating element for 3t .about.5t seconds, respectively. As a result, as shown in FIG. 17B of the accompanying drawings, pixels having different colored areas according to the respective densities are formed within one pixel interval in the direction in which the thermosensitive recording medium is fed (hereinafter referred to as a "feed direction"), thus recording a gradation image on the thermosensitive recording medium. In this example, the pixels shown in FIG. 17B are formed according to pulse-width modulation. However, the pixels shown in FIG. 17B may be formed according to pulse-number modulation.
When the gradation image is recorded on the thermosensitive recording medium in the above manner, each of the pixels starts being recorded from a point "a", with an unrecorded area left to a point "b" within the pixel interval in the feed direction. Therefore, the recorded image tends to concentrate on the side of the point "a". When the formed two-dimensional gradation image is observed in its entirety, it looks relatively coarse.